The operating temperature of gas turbines has been increasing year by year for the purpose of improving efficiency. To respond to such temperature increases, a coating layer for the purpose of heat shielding (thermal barrier coating: TBC) is formed on the surface of members for gas turbines exposed to high temperatures, for example, gas turbine blades, combustors.
Such coating layers are configured from an undercoating layer formed of an alloy on the base material of a member for gas turbines, and a top coating layer formed of a ceramic on the undercoating layer.
When repairing a member for gas turbines after operation, the coating layer formed on the base material of the member for gas turbines is peeled, and then a coating layer is regenerated by newly forming an undercoating layer and a top coating layer on the base material.
For example, as a method for peeling a coating layer, Patent Document 1 and Patent Document 2 disclose a method in which a member is immersed sequentially in an alkali washing solution, water, and a weak acid washing solution, and then, after heat treatment is performed, immersed in a strong acid washing solution (acidic aqueous solution).